Electrically driven clockwork



Aug. 1960 s. s. HELD 2,948,104

ELECTRICALLY DRIVEN CLOCKWORK Filed Dec. 9, 1955 2 Sheets-Sheet l Aug. 9 s. s. HELD 2,948,104

ELECTRICALLY DRIVEN CLOCKWORK Filed Dec. 9, 1955 2 Sheets-Sheet 2 Flam my H1113 F/G.14

T T E28 M H i 168 .f: A

Om {Md-on 2 $052. Sr' mon HELD United StatesPatent O ELECTRICALLY DRIVEN CLOCKWORK Serge Simon Held, 31 Rue de Chazelles, Paris 8e, France Filed Dec. 9, 1955, Ser. No. 552,192

Claims priority, application Switzerland June 6, 19-55 V 12 Claims. (CI. 58-28 The present invention relates to an electrical system for maintaining a cyclic motion of absolutely constant speed, such as the movement of the hands of a watch, clock, etc., with a circular balance and spiral spring (but which could just as well be applied to a pendular balance) and which operates indiiferently on direct or alternating current:

In order to obtain good isochronism, in the case of a circular balance to which this invention more particularly refers, it is necessary that the balance should oscillate freely over a wide angle and that the driving force be applied during a short time only, close to the position of static equilibrium, which is that in which the spiral spring has no torsion. The driving pulses should occur on either side of and as close as possible to the position of equilibrium; in the case of mechanical watches this is substantially accomplished by means of a lever and an escape wheel, which is regularised by the balance, to which it transmits two driving pulses in the direction of its displacement by means of inclined pallets. The balance acts as a regulator and oscillation counter and the energy it receives from the escape wheel is solely used for compensation of the losses due to the passive resistances it must overcome, the energy required for driving the mechanism being supplied by the mainspring. In the type of electric clock to be described, the balance fulfills the two functions of regulator and motor, in so far that it must drive the hands through a train of wheels at a speed in constant relation with its adjusted and strictly invariable oscillatory period. Thus, the energy which it receives at each oscillation must correspond to the whole movement, including that of the balance.

The systems put forward until now for electrically maintained clockwork with circular balance make use of a fixed electromagnet and a movable soft iron armature solid with the balance, or are built like a direct current galvanometer with a magnet and coil, either of which is fixed or movable. The present invention which does not make use of a fixed or movable magnet has all the advantages of simplicity, ruggedness and economy of electromagnetic systems, but differs essentially from them in its principle and by its advantages with respect to horological precision and preservation of contacts. In the known types, the fixed part comprises a small electromagnet acting by attraction on a soft iron armature acting as a balance, the coil of the electro-magnet being energized at the moment the balance closes the circuit of the battery by a contact. This electro-magnet has appreciable self-inductance and for this reason a spark is produced every time the circuit is opened and this, at length, deteriorates the contacts; the greater the specific energy stored in the iron, the more harm is done by the spark. It is therefore of advantage to reduce the size of the iron and of the coil, but one cannot carry this too far because of the reduced driving torque and, for the same reason, the moving armature cannot have too wide a gap. As the armature and also the electro-magnet retain a certain remanent magnetization after the current is broken, the oscillations of the balance are aifected with adverse eifects on its isochronism. The attraction produced for one direction of oscillation is, in general, suppressed for the other direction, in order not to impede the movement, and this requires the use of a special. unilateral contact. Systems have been proposed with a simple contact giving a driving pulse for one oscillation in both directions, the armature having a shape and position such that at each moment of contact it is equally attracted in both directions by two equal forces, the equilibrium being broken by the movement of the balance itself increasing the forces acting in the direction of its movement, but the inconvenience due to the immediate neighbourhood of a movable iron and a fixed electro-magnet remain. At the moment the contact is made, the driving torque, which is evidently null, increases and reaches a certain maximum, from which it then decreases. This maximum is only reached for a certain displacement of at least 45", whatever the proposed arrangements are, so that from the moment the contact ismade there is a waste of energy and then poor use of this energy because, unless the duration of contact is increased at the expense of the precision, this contact is broken before reaching the angular deviation which corresponds to maximum torque. It is evident that it would be of advantage to obtain the greatest torque value, on either side of the position of equilibrium, immediately, and a fraction of a second after the contact is made; in other words, that the torque curve be very steep followed by a sharp fall, in order that the top of the curve only be used for the duration of the contact, and this in one direction or the other, a condition which would be even better than that obtained in mechanical watches, in which, by construction, the two driving forces trans mitted to the balance do not coincide with its position of static equilibrium.

The requirements formulated above, i.e.

(1) practically insignificant influence of the remanence-(2) small volume of iron, low specific energy, very low self-inductance(3) obtainment of two driving pulses in opposite directions, of immediate growth, nearly exactly on the axis corresponding to the position of equilibrium, are realized in the present invention as described hereafter. The main idea is to use repulsion instead of attraction, repulsion which is produced between two bars or small plates of iron when they are magnetized in such manner that the poles of same name are face to face. The constructional arrangements adopted are such that for one position a very unstable equilibrium is obtained because, for the slightest displacement from this point, for an angle approximating 1, a driving force appears which immediately reaches its maximum and then decreases rapidly, said force acting the whole time in the direction of rotation of the balance. In practice, even in the static state, this equilibrium is so unstable that the irons are always in mutual repulsion so that such clockwork starts up immediately or spontaneously as soon as the current is switched on, without it being necessary to throw the balance as is required with all electrical clockworks of the double pulse type. The system described in this invention reproduces electrically, without material contact, the known mechanical arrangement of a striking hammer facing a heart-shaped cam which, starting from the wedge of the heart, can rotate in either direction, and in which the dead point (which would theoretically coincide with the position in which the point of the heart shaped cam would meet the ridge of the hammer) cannot occur in practice if the ridges are sharpenough.

Fig. 1 is a diagram showing the principle of the apparatus and the connections,

Fig. 2 shows an embodiment with magnetized irons in the shape of needles of circular or square cross-section.

Figs. 3 and 4 (perpendicular section along the axis and perspective) show another form of armature shaped from thin iron sheet, the profile being a portion of a cylinder.

Fig. 5 is a variant in which a pair of repulsive irons are located on a same diameter.

Fig. 6 illustrates a cross-section, parallel to the axis of rotation, of Fig. 2.

Figs. 7 and 8 are front and side views of cooperating movable and stationary iron members fitted in coils having parallel axes.

Fig. 9 shows a modification wherein the coils are coaxial.

Fig. 10 shows a further modification wherein the axes of the coils are parallel with the axis of the regulating system.

Fig. 11 shows a still further modification wherein two pairs of associated coils are located to either side of the axis of the regulating system.

Fig. 12 is a side view of a modification of Figs. 7 and 8.

These Figures 7 to 12 all show repulsive irons fitted directly in the windings so as to reduce the consumption of electric energy to a minimum.

Fig. 13 is a front view, and

Fig. 14 is a cross-section through the axis of rotation, of -a variant using two repulsive magnetic vanes enclosed in a flat coil, the vane moving in a plane parallel to the coil layers.

Figs. '15, cross-section perpendicular to the axis, and 16, cross-section parallel to the axis, show an improved embodiment with lower power consumption due to the increased proximity between the active layers of wire and the repulsive iron.

Figs. 17, 18 and 19 show different constructional arrangements derived from those of Figs. to 17.

In Fig. 1 M represents a circular winding of, for example, enamelled conducting wire, through the center part of which is a pivoted spindle carrying an elongated iron F highly permeable and without remanence, which moves opposite a fixed iron G fitted inside the coil and making a very small air gap with F -In practice, the winding is made on a very thin brass cylinder to the outside of which G is soldered before the solenoid winding is put on. it is obvious that the moving iron may be balanced by a counterweight and this assembly constitutes the actual balance, in combination with the regulating coil spring S. If the moment of inertia is not sufficient, a small round disc B of for example brass, may be fitted to the spindle; this disc carries a conducting pin g which makes contact with a flexible leaf 'Z in the position in which the two irons are in exact coincidence; the battery circuit is then closed through the coil M and the two irons magnetized. The polarities at the extremities then being of the same sign, the fixed iron repels the moving iron and, in the position of exact coincidence, the force thus created passes through the axis of rotation a. This position of equilibrium is very unstable as the two irons tend to repel each other. For a very small displacement to either side of the dead point, as soon as the movable iron has crossed the axis of coincidence of the centers of the two irons, in practice for a displacement equal to the thickness of one iron, a force is exerted on the balance. This force is substantially proportional to the square of the intensity and inversely proportional to the square ofthe distance between the two irons and lasts as long as the leaf-spring 1 remains in contact with pin g, i.e. for-an angle of about forty degrees from the neutral line. The leaf-spring l which, because of its elasticity, had remained in contact with pin g, then returns to its neutral .4 position on the dead line and the balance swings freely, driven by its kinetic energy until it reaches its position of maximum amplitude; from this point its direction of rotation reverses and contact is again established on the neutral line of unstable equilibrium of the irons, which is that in which their centers are in the same plane, and by reason of its throw the balance traverses the deadline and receives another pulse from the electromagnetic force, but in the reverse direction to the preceding one. The angular position in which contact is established is that corresponding to the position of static equilibrium of the balance, i.e. when torsion of the regulating spiral S is null, and it will be seen that the ideal conditions of operation for good isochronism are respected as, in accordance with horological technique,

two driving pulses are produced very close to and to in electro-magnetic apparatus of this type, when used for example as ammeters, because the square law functions render them insensitive to weak currents and the spacing of the irons with large deviations reduces the torque considerably, but it becomes an advantage in this horological application as the maximum current is provided immediately and the repelling effect is used only at the most favorable moment, i.e. that which occurs when the irons are very close to each other and repel each other strongly; in other words the two laws of proportionality of the force to the square of the current and to the inverse of the square of the distance between the irons answers the requirements exceedingly well, as well as the fact that with this arrangement one obtains a force acting in the direction of the movement for each direction of rotation of the balance.

Figures 3 and 4, which show respectively a crosssection perpendicular to the axis of rotation and a perspective view, represent the essential parts of a movable assemblage with two respulsive irons, F and G inthe shape of curved blades with a very small air-gap, the movable blade being solid with spindle a by means of a non-magnetic support A. Figure 5 is an electromagnetic assemblage based on the same principle but with a pair of repulsive irons F G F and G diametrically opposed; this arrangement provides amovable system which is balanced without the need of a counterweight, but which is more sensitive to remanence because this residual effect appears twice after each break of the current; this effect can howeverbe made practically negligible by the choice of a suitable hysteresis free iron. It is also possible to use two pairs of movable irons, instead of only one pair F F solid with the axis a. Fig. 6 is a cross-section through the axis of rotation, of the elements of the apparatus illustrated in Figs. 1 and 2.

Figures 7 to 12 refer "to an original and privileged embodiment of the invention, the main aim of which is to reduce the power requirements by winding the wire directly upon the actuating irons, without loss of space, which leads to lower ohmic resistance and to reduced volume of the irons in presence, so that the power characteristics closely approach those of moving coil instruments. Figure 7 (cross-section along the axis of rotation) illustrates as an example a constructional arrangement with a movable iron E in the shape of a letter U, with the axial part preferably reinforced, and surrounded by a solenoid winding M providing a very small 'air'gap; this enables magnetization of the irons with a fixed coil, the movable assemblage being very light. The fixed iron G has on the contrary a coil M wound directly upon the iron. Figure 8 illustrates an end view, from one side, of two of the repelling elements of the movable iron F and the fixed iron G It is to be noted that whatever the arrangement used it is of advantage to use identically shaped repelling elements and also that the flux be equal, in order to obtain a magnetic flow with divergent lines, as otherwise, one of the irons could have a preponderant effect and its flux would tend to flow in the other iron and produce an attracting force.

Figure 9 is a variant of Figures 7 and 8, and in which the repellent elements are constituted by two small irons F and G of, for example, cylindrical cross-section, the one being solid with the balance and the other fixed, the axis of the bars being placed diametrically with the poles of same sign passing face to face, being spaced as shown by a very small air gap. In order to reduce losses due to air flow, the irons should be flattened out in the direction of the axis, i.e. they should be oval-shaped. Figure 10 shows a variant with the irons F and G7 located parallel to the axis of rotation a, i.e. situated along the generating lines of the described cylinder; these irons are constituted by an elongated piece of soft iron.

of circular section placed along the axis, with small circular discs r -r at its ends, the coils being wound directly on the core to a thickness corresponding to the radius of the end discs which have the same diameter; the movable coil and the magnetized iron B; being fixed to the spindle of the balance by means of the clamp A. Figure 11 is based on the same principle as Figure 9, but with small iron elements having their axis parallel to the axis of rotation instead of perpendicular to said axis; by way of variant, two diagonally opposed stationary magnetizable elements G G and two magnetizable elements F F secured at D" to the spindle are shown and this does away with the necessity of equilibrating the balance by means of a small counterweight, as represented by j in Figure 9. It is obvious that following the same principle other forms of construction could be devised without leaving the scope of this invention; for example, in Figure 12, the irons F and G are of similar shape to that described for Figure 7 but are very flat and made from sheet iron, they may be situated face to face with the repulsive force acting on the edges of the end parts. If it is desired to retain the advantage of a single fixed polarizing coil, it is preferable to reduce as much as possible the clearance between the Wires of the fixed and movable irons in order to increase the useful torque and to decrease the consumption; it is evident that the field has its greatest intensity in the immediate vicinity of the wires. Figures 13 and 14 illustrate respectively a frontal View and a cross-section through the axis of rotation and show that the required conditions are met; M is a very flat coil, in two sections in order to provide a passage for the spindle, closely surrounding the fixed iron 6,, and the movable iron F which are made from sheeting cut to an oval or elliptical shape, the plane of which is perpendicular to the axis of rotation. In the position occurring when contact is made, the two surfaces are exactly face to face and the transversal dimensions of the coil are such as to allow free rotation with minimum spacing. This arrangement, which would be unsatisfactory for electro-magnetic measuring instruments because of the scale distortion and sharp decrease of torque, is, on the other hand, very favorable for the maintenance of oscillations, because the current is broken for a small displacement on either side of the position of equilibrium or deadpoint. In the same way, Figures 15 and 16 which are respectively an end view along the axis and a cross-section through the axis of rotation, represent an outer circular winding N and an inner winding N in which the current flow is indicated by the arrow X and X the twowindings demarcate a small annular space in which the movable iron F can slide whilst iron G is located on the inner lining; it will be seen that under these conditions the adjacent parts of the windings create fluxes which add, just as if we were considering the two parallel sides of an unbroken frame winding. There results therefrom an increase of the magnetizing flux which, from this point of view, gives an advantage over the constructional arrangement with a single coil as described for the Figures 1 to 4. It is also possible to use two arms K pivotally mounted around the axis a and each carrying two irons F and F As has already been noted, the useful action of the repelling irons is produced for a small displacement, or, in other words, for a small mutual displacement with respect to the fully overlapping position. It is possible to form a combination of juxtaposed fiat coils, using only those layers which provide additive or converging fluxes, such as shown in cross-section in Figure 17, in which use is made of two pairs of coils L L' and L 'L arranged side by side, the direction of flow of the flux being indicated by the arrows; it is thus possible to obtain a strong polarisation of the irons F and G during the full contact time, exactly as if we were considering an enveloping coil as shown in Figure 18 in which Q and Q represent two parts of coil layers fed with mutually reversed currents. As these layers belong to two different coils they are not interconnected, as would be the case with a single winding, by the wires shown in broken lines in Figure 18, and there is no obstruction at the ends of the layers;'in this way the movable iron can slide freely under the influence of two layers of wires which are very close to each other and thus produce a particularly efficient polarizing action. As the movable iron is revoluble around an axis, it is possible to form a group of coils such as L and L of Figure 17 in the shape indicated in Figure 19 and the active layers, at the moment contact is made, are represented by the assemblage Q Q it being understood that the irons are in the position shown, and juxtaposed, at the moment contact is made.

One of the qualities of the maintaining system that has been described, system operating by virtue of the repulsion between juxtaposed pin-point surfaces, is the generation of an actuating force in the direction of the oscillation at the instant the two irons are no longer in exact coincidence, that is to say, are slightly displaced to either side of the unstable balance point. In other words, the unstable balance position is very critical and equilibrium is upset as soon as the centers of the irons are out of coincidence; it is only in this position of coincidence that the repelling force passes through the axis and is cancelled out by the reaction of the supporting elements. A tangential component appears as soon as the neutral line is overshot, the force of inertia of the balance being sufficient to take it through the unstable position of equilibrium.

It is to be noted that any elfects due to rem'anence are practically insignificant because of the smallness of the irons and of their remoteness from the center of rotation; should there be any such effects, the influence would only be felt when the irons are very close together in the region where contact is established, i.e. the position of static equilibrium of the hair-spring, for which the passive or active forces have very little effect on the isochronism of the balance. For a displacement of about ten degrees from the neutral line, the residual magnetization has very little effect because repulsion decreases with the square of the distance and,'in view of the smallness of the active surface in presence, the remoteness of the irons becomes relatively considerable.

The mechanical outlay of the motion-work itself, or that of the mechanism used for transforming the oscillat ing mot-ion of the balance wheel to rotation of the same direction as that of the first wheel of the gearing which drives the hands of the clock, are not described, because '7 these well-known means do not fall within the scope of this invention.

It is anticipated in this invention to use a potentiometric resistance in the circuit provided for alternating current supplies in order to reduce the voltage to that of the batteries used with direct current supplies.

Thus, simply by changing over the connecting wires, it is possible for the clockwork to operate from AC. or DC. sources. The magnetizing winding and the contact are fed from a fraction of the resistance connected to the high voltage source in such a manner that the current is broken under the same conditions as with direct current, i.e. at a voltage of 1.5 to 2 volts for example.

What I claim is:

1. In an electrically driven clockwork including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contact-piece carried by the balance and a stationary contact-piece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding the convolutions of which lie on a cylindrical surface coaxial with the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contact-piece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending along the axis of the windingand two similar elongated soft iron bars, extending in parallelism with said spindle and of which one is rigid with the spindle and the other is stationary and lies substantially along a generating line of its cylindrical surface very near the locus of the bar rigid with the spindle, said bars being simultaneously magnetized and repelling each other during the short energization of the winding obtained by the closing of the switch in said position of non-stable equilibrium.

2. In an electrically driven clockwork, including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contactpiece carried by the balance and a stationary contactpiece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on at least one cylindrical surface, the axis of which is perpendicular to the plane of the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contact-piece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending coaxially with said cylindrical surface of the winding and at least one pair of similar elongated soft iron bars, at least the ends of which lie in proximity with said cylindrical surface, of which bars one is rigid with the spindle and extends in a plane radial with reference thereto and the other is stationary and lies very near the locus of the bar rigid with the spindle in a plane radial with reference to the spindle axis and registering substantially with the first radial plane for said position of non-stable equilibrium, said bars lying in adjacent relationship to be simultaneously magnetized by the winding and to repel each other during the short energization of said winding obtained by the closing of the switch in said position of non-stable equilibrium.

3. In an electrically driven clockwork including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply; a switch including a movable contactpiece carried by the balance and a stationary contact-piece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on a cylindrical surface coaxial with the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through themovable con tact-piece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending along the axis of the winding and two similar elongated soft iron bars extending in parallelism with said spindle with in said winding very close the cylindrical surface at slightly different radial distances from the axis of said surface, and of which bars one is rigid with the spindle and the other is stationary and lies substantially along a generating line of said cylindrical surface very near the locus of the bar rigid with the spindle, said bars being simultaneously magnetized and repelling each other during the short energization of the winding obtained by the closing of the switch in said position of non-stable equilibrium.

4. In an electrically driven clockwork, including an oscillating balance adapted to oscillate to either side of a position of non stable equilibrium; the combination of a power supply, a switch including a movable contactpiece carried by the balance and a stationary contact-piece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on two separate cylindrical surfaces, the axes of which are perpendicular to the plane of the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contact-piece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending coaxially with the said cylindrical surface of the winding and at least one pair of similar elongated soft iron bars, at least the ends of which lie in proximity with said cylindrical surface, of which bars one is rigid with the spindle and extends in a plane radial with reference thereto and the other is stationary and lies very near the locus of the bar rigid with the spindle in a plane radial with reference to the spindle axis and registering substantially with the first radial plane for said position of non-stable equilibrium, said bars lying in adjacent relationship to be simultaneously magnetized by the winding and to repel each other during the short energization of said winding obtained by the closing of the switch in said position of non-stable equilibrium.

5. In an electrically driven clockwork including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contactpiece carried by the balance and a stationary contact-piece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding the convolutions of which lie on a cylindrical surface coaxial with the "balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contactpiece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending along the axis of the winding and two similar elongated soft iron bars, having a flat rectangular cross-section extending in parallelism with said spindle and of which bars one is rigid with the spindle and the other is stationary and lies substantially along a generating line of said cylindrical surface very near the locus of the bar rigid with the spindle, said bars being simultaneously magnetized and repelling each other during the short energization of the winding obtained by the closing of the switch in said position of non-stable equilibrium.

6. In an electrically driven clockwork as claimed in claim 1, the provision of two further elongated soft iron bars similar to the first-mentioned bars extending in parallelism with said spindle and diametrically opposed to the first mentioned bars with reference to the winding and of which one is rigid with the spindle and the other is stationary, said last-mentioned further bars lying at radial distances from the axis of the winding which are equal to the radial distances of the corresponding firstmentioned iron bars.

,7. In an electrically driven clockwork, including an 9 oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contactpiece carried by the balance and a stationary contact-piece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on atleast one cylindrical surface the axis of which is perpendicular to the plane of the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contact-piece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending coaxially with the said cylindrical surface of the winding and at least one pair of similar elongated soft iron bars, at least the ends of which lie in proximity with said cylindrical surface of which bars one is rigid with the spindle and extends perpendicularly to the latter in a plane radial with reference thereto and the other is stationary and lies very near the locus of the bar rigid with the spindle and radially with reference to said spindle, said bars lying in adjacent relationship for said position of non-stable equilibriumto be simultaneously magnetized by the winding and to repel each other during the short energization of said winding obtained by the closing of the switch in said position of non-stable equilibrium.

'8. In an electrically driven clockwork, including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contactpiece carried by the balance and a stationary contactpiece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on at least one cylindrical surface, the axis of which is perpendicular to the plane of the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contact-piece in said position 'of non-stable equilibrium, a rotary spindle rigid with the balance and extending coaxially with said cylindrical surface of the winding and two U-shaped bars having their branches extending into proximity with said cylindrical surface, of which bars one is rigid with the spindle and extends in a plane radial with reference thereto and the other is stationary and has its ends very near the locus of the bar rigid with the spindle in a plane radial with reference to the spindle axis and registering substantially with the first radial plane for said position of non-stable equilibrium, said bars lying in adjacent relationship to be simultaneously magnetized by the winding and to repel each other during the short energization of said winding obtained by the closing of the switch in said position of non-stable equilibrium.

9. In. an electrically driven clockwork, including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contact-piece carried by the balance and a stationary contact-piece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on two surfaces coaxial with the spindle and separated by a narrow gap perpendicular to the plane of the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contact-piece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending coaxially with said cylindrical surface of the winding and two pairs of soft iron bars parallel with the spindle, arranged in diametrically opposed relationship with reference to the latter inside the and the other is stationary and lies very near the locus of the bar rigid with the spindle in a plane radial with reference to the spindle axis and registering substantially with the first radial plane for said positionof nonstable equilibrium, said bars lying in adjacent relationship to be simultaneously magnetized by the winding and to repel each other during the short energization of said winding obtained by the closing of the switch in saidposition of non-stable equilibrium.

10. In an electrically driven clockwork, including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contactpiece carried by the balance and a stationary contactpiece engaged by the movable contact piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on two cylindrical surfaces, the first of which has its axis parallel with that of the balance and the second surface has its axis coinciding with the axis of the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contact-piece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending coaxially with said cylindrical surface of the winding and two similar stationary iron bars extending inside the corresponding cylindrical surfaces of the winding in close proximity with said surfaces in parallelism with the spindle, of which bars that contained inside the second cylindrical surface is rigid with the spindle and the other is stationary and lies very near the locus of the bar rigid with the spindle, said bars lying in adjacent relationship for said position of nonstable equilibrium to be simultaneously magnetized by the winding and to repel each other during the short energization of said winding obtained by the closing of the switch.

11. In an electrically driven clockwork, including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contactpiece carried by the balance and a stationary contactpiece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on two cylindrical surfaces, one of which has its axis parallel with that of the balance and the other has its axis coinciding with said axis of the balance, said winding connecting the power supply with the stationary contact-piece to close the circuit through the movable contact-piece in said position of non-stable equilibrium, a rotary spindle rigid with the balance and extending coaxially with said cylindrical surface of the winding and a stationary U-shaped soft iron bar extending inside the first cylindrical surface of the winding and having its arms projecting in the plane containing the axes of the two cylindrical surfaces in a direction radial with reference to the spindle, a U-shaped soft iron bar rigid with the spindle and extending inside the second cylindrical surface with its arms extending radially of said spindle to face the corresponding arms of the first-mentioned U-shaped bar with a very small gap therebetween for said position of non-stable equilibrium to be simultaneously magnetized by the winding and to repel each other during the short energization of said winding obtained by the closing of the switch.

12. In an electrically driven clockwork, including an oscillating balance adapted to oscillate to either side of a position of non-stable equilibrium, the combination of a power supply, a switch including a movable contactpiece carried by the balance and a stationary contactpiece engaged by the movable contact-piece in said position of non-stable equilibrium, a circuit fed by the power supply and including a winding, the convolutions of which lie on at least one cylindrical surface, the ax s 1 1 1 2 of which is perpendicular to the plane of the balance, relationship to be simultaneously magnetized by the said winding connecting the power supply with the stawinding and to repel each other during the short enertionary contact-piece to close the circuit through the gization of said winding obtained by the closing of the movable contact-piece in said position of non-stable switch in said position of non-stable equilibrium. equilibrium, a rotary spindle rigid with the balance and 5 extending coaxially with said cylindrical surface of the References Cited in the file of this patent winding and at least one pair of similar elongated soft iron bars, at least the ends of which lie in proximity UNITED STATES PATENTS with said cylindrical surface, of which bars one is rigid 1,991,839 Y j 1935 with the spindle and extends radially with reference 10 2,240,927 Gelsshngel' May 61 1941 thereto and the other is stationary and lies very near the locus of the bar rigid with the Spindle radially with FOREIGN PATENTS reference to the spindle axis, said bars lying in adjacent 1,009,776 France Mar. 12, 1952 

